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A banking trojan, known for its small size but powerful capabilities, has expanded the number of financial institutions it can collect data from, according to security vendor Avast.

Tiny Banker, also known as Tinba, was discovered around mid-2012 after it infected thousands of computers in Turkey.

The malware is just 20K in size and can inject HTML fields into websites when it detects a user has navigated to a banking site, asking for a range of sensitive information banks would never request during an online session.

A version analyzed by Avast showed Tiny Banker has been customized to target many new financial institutions, many of which are based in the U.S. such as Wells Fargo, Bank of America and Chase, wrote Jaromir Horejsi, an Avast malware analyst.

A screenshot bearing Wells Fargo’s logo showed how Tiny Banker asks for more information when a person logs into their account. It shows a bogus warning about a system update, asking users to provider more information to verify their identity.

The requested information includes a card number, expiration date, the three digit security code on the back of a card, a person’s address, Social Security number, date of birth, mother’s maiden name and driver’s license number and its expiration.

Tiny Banker has now been seen distributed by the Rig exploit kit, Horejsi wrote. Exploit kits are packages of software planted on websites that attack visitors’ computers, looking for software vulnerabilities and delivering malware if one is found.

The revisions to Tiny Banker comes after its source code was leaked in early July, which may have seen it embraced by cybercriminals who could use it without paying for it, as many such programs are sold.

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